Study: Long-term smoking leads to cognitive decline

Smokers had thinner brain cortex than those that never smoked.

Smoking (photo credit: INGIMAGE / ASAP)
(photo credit: INGIMAGE / ASAP)
The bad news is that if you have been smoking for years, you may have caused the thinning of the cerebral cortex – a vital part of your brain.
The cortex is the outer layer of the brain in which critical cognitive functions such as memory, language and perception take place, and a thinner brain cortex is associated with adult cognitive decline.
The good news is that if you kick the habit now, you may make it possible for your body to restore at least part of the thickness of the cortex.
But the apparent recovery process is slow and incomplete, as heavy ex-smokers in a study who had given up smoking for more than 25 years still had a thinner cortex. The study was published on Tuesday in the online version of the journal Molecular Psychiatry.
Researchers in Montreal studied 244 male and 260 female subjects – group five times larger than any previous similar research on smoking and cortical thickness – with an average age of 73. The test group included current smokers, ex-smokers and non-smokers.
All of the subjects were examined as children in 1947 as part of the Scottish Mental Survey.
Researchers used health data gathered during recent personal interviews with the subjects and analyzed data from MRI scans showing the current state of their cortex.
“We found that current and ex-smokers had many areas of thinner brain cortex than those that never smoked. Subjects who stopped smoking seem to partially recover their cortical thickness for each year without smoking,” said lead author psychiatry professor Sherif Karama of McGill University and the Douglas Mental Health University Institute.
Although the cortex grows thinner with normal aging, the study found that smoking appears to accelerate the thinning process. “Smokers should be informed that cigarettes could hasten the thinning of the brain’s cortex, which could lead to cognitive deterioration.
Cortical thinning seems to persist for many years after someone stops smoking, declared Karama.
Asked to comment, Prof. Ben- Amir Sela – director of Sheba Medical Center’s institute of chemical pathology and a member of the biochemistry department at Tel Aviv University – said that coming after a host of studies corroborating the many forms of harm tobacco causes, “This is incredibly impressive if the data can be duplicated by other groups of neurologists and on larger groups of people.”
Sela has written hundreds of scientific and educational articles on the dangers of tobacco, as well as on biology and medicine and published them on the website Teva Life (
Tobacco use has been associated for some time with cognitive decline and dementia, the authors wrote, “but the extent of the association between smoking and structural brain changes remained unclear.
Importantly, it is unknown whether smoking-related brain changes are reversible after smoking cessation.” It is estimated that nearly 14 percent of Alzheimer’s disease cases worldwide could be attributable to smoking.
“Smokers need to be informed that cigarettes are associated with accelerated cortical thinning – a biomarker of cognitive aging. Importantly, cortical thinning can persist for many years after smoking cessation,” the authors concluded. “The potential to at least partially recover from smoking-related thinning might serve as a strong motivational argument to encourage smoking cessation.”